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1 /* $OpenBSD: kex.h,v 1.81 2016/09/28 21:44:52 djm Exp $ */
2 
3 /*
4  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 #ifndef KEX_H
27 #define KEX_H
28 
29 #include "mac.h"
30 #include "buffer.h" /* XXX for typedef */
31 #include "key.h" /* XXX for typedef */
32 
33 #ifdef WITH_LEAKMALLOC
34 #include "leakmalloc.h"
35 #endif
36 
37 #ifdef WITH_OPENSSL
38 # ifdef OPENSSL_HAS_ECC
39 #  include <openssl/ec.h>
40 # else /* OPENSSL_HAS_ECC */
41 #  define EC_KEY	void
42 #  define EC_GROUP	void
43 #  define EC_POINT	void
44 # endif /* OPENSSL_HAS_ECC */
45 #else /* WITH_OPENSSL */
46 # define EC_KEY		void
47 # define EC_GROUP	void
48 # define EC_POINT	void
49 #endif /* WITH_OPENSSL */
50 
51 #define KEX_COOKIE_LEN	16
52 
53 #define	KEX_DH1				"diffie-hellman-group1-sha1"
54 #define	KEX_DH14_SHA1			"diffie-hellman-group14-sha1"
55 #define	KEX_DH14_SHA256			"diffie-hellman-group14-sha256"
56 #define	KEX_DH16_SHA512			"diffie-hellman-group16-sha512"
57 #define	KEX_DH18_SHA512			"diffie-hellman-group18-sha512"
58 #define	KEX_DHGEX_SHA1			"diffie-hellman-group-exchange-sha1"
59 #define	KEX_DHGEX_SHA256		"diffie-hellman-group-exchange-sha256"
60 #define	KEX_ECDH_SHA2_NISTP256		"ecdh-sha2-nistp256"
61 #define	KEX_ECDH_SHA2_NISTP384		"ecdh-sha2-nistp384"
62 #define	KEX_ECDH_SHA2_NISTP521		"ecdh-sha2-nistp521"
63 #define	KEX_CURVE25519_SHA256		"curve25519-sha256"
64 #define	KEX_CURVE25519_SHA256_OLD	"curve25519-sha256@libssh.org"
65 
66 #define COMP_NONE	0
67 #define COMP_ZLIB	1
68 #define COMP_DELAYED	2
69 
70 #define CURVE25519_SIZE 32
71 
72 enum kex_init_proposals {
73 	PROPOSAL_KEX_ALGS,
74 	PROPOSAL_SERVER_HOST_KEY_ALGS,
75 	PROPOSAL_ENC_ALGS_CTOS,
76 	PROPOSAL_ENC_ALGS_STOC,
77 	PROPOSAL_MAC_ALGS_CTOS,
78 	PROPOSAL_MAC_ALGS_STOC,
79 	PROPOSAL_COMP_ALGS_CTOS,
80 	PROPOSAL_COMP_ALGS_STOC,
81 	PROPOSAL_LANG_CTOS,
82 	PROPOSAL_LANG_STOC,
83 	PROPOSAL_MAX
84 };
85 
86 enum kex_modes {
87 	MODE_IN,
88 	MODE_OUT,
89 	MODE_MAX
90 };
91 
92 enum kex_exchange {
93 	KEX_DH_GRP1_SHA1,
94 	KEX_DH_GRP14_SHA1,
95 	KEX_DH_GRP14_SHA256,
96 	KEX_DH_GRP16_SHA512,
97 	KEX_DH_GRP18_SHA512,
98 	KEX_DH_GEX_SHA1,
99 	KEX_DH_GEX_SHA256,
100 	KEX_ECDH_SHA2,
101 	KEX_C25519_SHA256,
102 	KEX_MAX
103 };
104 
105 #define KEX_INIT_SENT	0x0001
106 
107 struct sshenc {
108 	char	*name;
109 	const struct sshcipher *cipher;
110 	int	enabled;
111 	u_int	key_len;
112 	u_int	iv_len;
113 	u_int	block_size;
114 	u_char	*key;
115 	u_char	*iv;
116 };
117 struct sshcomp {
118 	u_int	type;
119 	int	enabled;
120 	char	*name;
121 };
122 struct newkeys {
123 	struct sshenc	enc;
124 	struct sshmac	mac;
125 	struct sshcomp  comp;
126 };
127 
128 struct ssh;
129 
130 struct kex {
131 	u_char	*session_id;
132 	size_t	session_id_len;
133 	struct newkeys	*newkeys[MODE_MAX];
134 	u_int	we_need;
135 	u_int	dh_need;
136 	int	server;
137 	char	*name;
138 	char	*hostkey_alg;
139 	int	hostkey_type;
140 	int	hostkey_nid;
141 	u_int	kex_type;
142 	int	rsa_sha2;
143 	int	ext_info_c;
144 	struct sshbuf *my;
145 	struct sshbuf *peer;
146 	sig_atomic_t done;
147 	u_int	flags;
148 	int	hash_alg;
149 	int	ec_nid;
150 	char	*client_version_string;
151 	char	*server_version_string;
152 	char	*failed_choice;
153 	int	(*verify_host_key)(struct sshkey *, struct ssh *);
154 	struct sshkey *(*load_host_public_key)(int, int, struct ssh *);
155 	struct sshkey *(*load_host_private_key)(int, int, struct ssh *);
156 	int	(*host_key_index)(struct sshkey *, int, struct ssh *);
157 	int	(*sign)(struct sshkey *, struct sshkey *, u_char **, size_t *,
158 	    const u_char *, size_t, const char *, u_int);
159 	int	(*kex[KEX_MAX])(struct ssh *);
160 	/* kex specific state */
161 	DH	*dh;			/* DH */
162 	u_int	min, max, nbits;	/* GEX */
163 	EC_KEY	*ec_client_key;		/* ECDH */
164 	const EC_GROUP *ec_group;	/* ECDH */
165 	u_char c25519_client_key[CURVE25519_SIZE]; /* 25519 */
166 	u_char c25519_client_pubkey[CURVE25519_SIZE]; /* 25519 */
167 };
168 
169 int	 kex_names_valid(const char *);
170 char	*kex_alg_list(char);
171 char	*kex_names_cat(const char *, const char *);
172 int	 kex_assemble_names(const char *, char **);
173 
174 int	 kex_new(struct ssh *, char *[PROPOSAL_MAX], struct kex **);
175 int	 kex_setup(struct ssh *, char *[PROPOSAL_MAX]);
176 void	 kex_free_newkeys(struct newkeys *);
177 void	 kex_free(struct kex *);
178 
179 int	 kex_buf2prop(struct sshbuf *, int *, char ***);
180 int	 kex_prop2buf(struct sshbuf *, char *proposal[PROPOSAL_MAX]);
181 void	 kex_prop_free(char **);
182 
183 int	 kex_send_kexinit(struct ssh *);
184 int	 kex_input_kexinit(int, u_int32_t, void *);
185 int	 kex_input_ext_info(int, u_int32_t, void *);
186 int	 kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *);
187 int	 kex_derive_keys_bn(struct ssh *, u_char *, u_int, const BIGNUM *);
188 int	 kex_send_newkeys(struct ssh *);
189 int	 kex_start_rekex(struct ssh *);
190 
191 int	 kexdh_client(struct ssh *);
192 int	 kexdh_server(struct ssh *);
193 int	 kexgex_client(struct ssh *);
194 int	 kexgex_server(struct ssh *);
195 int	 kexecdh_client(struct ssh *);
196 int	 kexecdh_server(struct ssh *);
197 int	 kexc25519_client(struct ssh *);
198 int	 kexc25519_server(struct ssh *);
199 
200 int	 kex_dh_hash(int, const char *, const char *,
201     const u_char *, size_t, const u_char *, size_t, const u_char *, size_t,
202     const BIGNUM *, const BIGNUM *, const BIGNUM *, u_char *, size_t *);
203 
204 int	 kexgex_hash(int, const char *, const char *,
205     const u_char *, size_t, const u_char *, size_t, const u_char *, size_t,
206     int, int, int,
207     const BIGNUM *, const BIGNUM *, const BIGNUM *,
208     const BIGNUM *, const BIGNUM *,
209     u_char *, size_t *);
210 
211 int kex_ecdh_hash(int, const EC_GROUP *, const char *, const char *,
212     const u_char *, size_t, const u_char *, size_t, const u_char *, size_t,
213     const EC_POINT *, const EC_POINT *, const BIGNUM *, u_char *, size_t *);
214 
215 int	 kex_c25519_hash(int, const char *, const char *,
216     const u_char *, size_t, const u_char *, size_t,
217     const u_char *, size_t, const u_char *, const u_char *,
218     const u_char *, size_t, u_char *, size_t *);
219 
220 void	kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
221 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
222 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
223 int	kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
224     const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
225 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
226 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
227 
228 int
229 derive_ssh1_session_id(BIGNUM *, BIGNUM *, u_int8_t[8], u_int8_t[16]);
230 
231 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
232 void	dump_digest(char *, u_char *, int);
233 #endif
234 
235 #if !defined(WITH_OPENSSL) || !defined(OPENSSL_HAS_ECC)
236 # undef EC_KEY
237 # undef EC_GROUP
238 # undef EC_POINT
239 #endif
240 
241 #endif
242